我一直在https://github.com/codepath/android_guides/wiki/Building-Simple-Chat-Client-with-Parse关注如何使用parse.com构建一个简单的聊天客户端的本教程。我已完成教程，现在当您发送消息时，它会将消息发送给拥有该应用的任何人。如何制作以便用户可以选择收件人？我的聊天客户端代码与上面教程中的代码相同。
以下是我的RecipientsActivity代码
public class RecipientsActivity extends Activity {
public static final String TAG = RecipientsActivity.class.getSimpleName();
protected ParseRelation<ParseUser> mFriendsRelation;
protected ParseUser mCurrentUser;
protected List<ParseUser> mFriends;
protected MenuItem mSendMenuItem;
protected Uri mMediaUri;
protected String mFileType;
protected GridView mGridView;
protected String mTextMessage;
protected int mMemeImage;
protected String mTextTop;
protected String mTextBottom;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
setContentView(R.layout.user_grid);
// Show the Up button in the action bar.
setupActionBar();
mGridView = (GridView) findViewById(R.id.friendsGrid);
mGridView.setChoiceMode(AbsListView.CHOICE_MODE_MULTIPLE);
mGridView.setOnItemClickListener(mOnItemClickListener);
TextView emptyTextView = (TextView) findViewById(android.R.id.empty);
mGridView.setEmptyView(emptyTextView);
mFileType = getIntent().getExtras().getString(
ParseConstants.KEY_FILE_TYPE);
if (mFileType.equals(ParseConstants.TYPE_TEXT_MESSAGE)) {
mTextMessage = getIntent().getExtras().getString(
ParseConstants.KEY_TEXT);
}
else if (mFileType.equals(ParseConstants.TYPE_MEME)) {
mMemeImage = getIntent().getExtras().getInt(
ParseConstants.KEY_MEME_IMAGE);
mTextTop = getIntent().getExtras().getString(
ParseConstants.KEY_MEME_TOP_TEXT);
mTextBottom = getIntent().getExtras().getString(
ParseConstants.KEY_MEME_BOTTOM_TEXT);
}
else {
mMediaUri = getIntent().getData();
}
}
@Override
public void onResume() {
super.onResume();
mCurrentUser = ParseUser.getCurrentUser();
mFriendsRelation = mCurrentUser
.getRelation(ParseConstants.KEY_FRIENDS_RELATION);
setProgressBarIndeterminateVisibility(true);
ParseQuery<ParseUser> query = mFriendsRelation.getQuery();
query.addAscendingOrder(ParseConstants.KEY_USERNAME);
query.findInBackground(new FindCallback<ParseUser>() {
@Override
public void done(List<ParseUser> friends, ParseException e) {
setProgressBarIndeterminateVisibility(false);
if (e == null) {
mFriends = friends;
String[] usernames = new String[mFriends.size()];
int i = 0;
for (ParseUser user : mFriends) {
usernames[i] = user.getUsername();
i++;
}
if (mGridView.getAdapter() == null) {
UserAdapter adapter = new UserAdapter(
RecipientsActivity.this, mFriends);
mGridView.setAdapter(adapter);
} else {
((UserAdapter) mGridView.getAdapter()).refill(mFriends);
}
} else {
Log.e(TAG, e.getMessage());
AlertDialog.Builder builder = new AlertDialog.Builder(
RecipientsActivity.this);
builder.setMessage(e.getMessage())
.setTitle(R.string.error_title)
.setPositiveButton(android.R.string.ok, null);
AlertDialog dialog = builder.create();
dialog.show();
}
}
});
}
/**
* Set up the {@link android.app.ActionBar}.
*/
private void setupActionBar() {
getActionBar().setDisplayHomeAsUpEnabled(true);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.recipients, menu);
mSendMenuItem = menu.getItem(0);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
// This ID represents the Home or Up button. In the case of this
// activity, the Up button is shown. Use NavUtils to allow users
// to navigate up one level in the application structure. For
// more details, see the Navigation pattern on Android Design:
//
// http://developer.android.com/design/patterns/navigation.html#up-vs-back
//
NavUtils.navigateUpFromSameTask(this);
return true;
case R.id.action_send:
ParseObject message = createMessage();
if (message == null) {
// error
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage(R.string.error_selecting_file)
.setTitle(R.string.error_selecting_file_title)
.setPositiveButton(android.R.string.ok, null);
AlertDialog dialog = builder.create();
dialog.show();
} else {
send(message);
finish();
}
return true;
}
return super.onOptionsItemSelected(item);
}
protected ParseObject createMessage() {
ParseObject message = new ParseObject(ParseConstants.CLASS_MESSAGES);
message.put(ParseConstants.KEY_SENDER_ID, ParseUser.getCurrentUser()
.getObjectId());
message.put(ParseConstants.KEY_SENDER_NAME, ParseUser.getCurrentUser()
.getUsername());
message.put(ParseConstants.KEY_RECIPIENT_IDS, getRecipientIds());
message.put(ParseConstants.KEY_FILE_TYPE, mFileType);
if (mFileType.equals(ParseConstants.TYPE_TEXT_MESSAGE)) {
message.put(ParseConstants.KEY_TEXT, mTextMessage);
} else if (mFileType.equals(ParseConstants.TYPE_MEME)) {
message.put(ParseConstants.KEY_MEME_IMAGE, mMemeImage);
message.put(ParseConstants.KEY_MEME_TOP_TEXT, mTextTop);
message.put(ParseConstants.KEY_MEME_BOTTOM_TEXT, mTextBottom);
}
else {
// Process and attach media file
byte[] fileBytes = FileHelper.getByteArrayFromFile(this, mMediaUri);
if (fileBytes == null) {
return null;
} else {
if (mFileType.equals(ParseConstants.TYPE_IMAGE)) {
fileBytes = FileHelper.reduceImageForUpload(fileBytes);
}
String fileName = FileHelper.getFileName(this, mMediaUri,
mFileType);
ParseFile file = new ParseFile(fileName, fileBytes);
message.put(ParseConstants.KEY_FILE, file);
return message;
}
}
return message;
}
protected ArrayList<String> getRecipientIds() {
ArrayList<String> recipientIds = new ArrayList<String>();
for (int i = 0; i < mGridView.getCount(); i++) {
if (mGridView.isItemChecked(i)) {
recipientIds.add(mFriends.get(i).getObjectId());
}
}
return recipientIds;
}
protected void send(ParseObject message) {
message.saveInBackground(new SaveCallback() {
@Override
public void done(ParseException e) {
if (e == null) {
// success!
Toast.makeText(RecipientsActivity.this,
R.string.success_message, Toast.LENGTH_LONG).show();
sendPushNotifications();
} else {
AlertDialog.Builder builder = new AlertDialog.Builder(
RecipientsActivity.this);
builder.setMessage(R.string.error_sending_message)
.setTitle(R.string.error_selecting_file_title)
.setPositiveButton(android.R.string.ok, null);
AlertDialog dialog = builder.create();
dialog.show();
}
}
});
}
protected OnItemClickListener mOnItemClickListener = new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
if (mGridView.getCheckedItemCount() > 0) {
mSendMenuItem.setVisible(true);
} else {
mSendMenuItem.setVisible(false);
}
ImageView checkImageView = (ImageView) view
.findViewById(R.id.checkImageView);
if (mGridView.isItemChecked(position)) {
// add the recipient
checkImageView.setVisibility(View.VISIBLE);
} else {
// remove the recipient
checkImageView.setVisibility(View.INVISIBLE);
}
}
};
protected void sendPushNotifications() {
ParseQuery<ParseInstallation> query = ParseInstallation.getQuery();
query.whereContainedIn(ParseConstants.KEY_USER_ID, getRecipientIds());
// send push notification
ParsePush push = new ParsePush();
push.setQuery(query);
push.setMessage(getString(R.string.push_message, ParseUser
.getCurrentUser().getUsername()));
push.sendInBackground();
}
}